Downhole Friction Control Systems and Methods

ABSTRACT

A downhole friction control system comprises a downhole sub to attach to a drill string and a vibration component. The vibration component is mechanically coupled to the downhole sub to generate a selected vibration in the drill string when the downhole sub is attached to the drill string. Additional apparatus, methods, and systems are disclosed.

BACKGROUND

Downhole friction often interferes with the operation of downhole tools.In some cases, friction arises due to the presence of dirt, sand,concrete, debris, or other solids in downhole fluids. While someconventional systems attempt to prevent the accumulation of debris, theyfail to provide relief once debris or solids begin interfering with theoperation of the tool. These accumulated solids can be difficult, if notimpossible, to remove with conventional filter systems that cannot becleaned or unplugged. Downhole friction can also occur as a result oftight tolerances, drag caused by sealing surfaces, or the use ofdownhole tools against rough surfaces, such as a downhole cutting tool.When a tool encounters issues associated with downhole friction,conventional methods to overcome the friction involve applyingadditional pressure to the tool, which can lead to tool degradation anddamage.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousfeatures and advantages made apparent to those of ordinary skill in theart by referencing the accompanying drawings. The use of the samereference symbols in different drawings indicates similar or identicalitems.

FIG. 1 depicts an example downhole friction control system, inaccordance with some embodiments.

FIG. 2 depicts an example downhole friction control system in use with aball valve in a closed position, in accordance with some embodiments.

FIG. 3 depicts the example downhole friction control system of FIG. 2with the ball valve in the open position, in accordance with someembodiments.

FIG. 4 is a flow diagram of an example method of downhole frictioncontrol, in accordance with some embodiments.

FIG. 5 depicts an example system at a wireline site, in accordance withsome embodiments.

FIG. 6 depicts an example system at a drilling site, in accordance withsome embodiments.

DETAILED DESCRIPTION

FIG. 1 depicts an example downhole friction control system 100, inaccordance with some embodiments. The downhole friction control system100 generally comprises a downhole sub 102 to attach to a drill string104 to be placed in a wellbore 106. In some embodiments, the downholefriction control system 100 further comprises a downhole tool 108coupled to the drill string. While the illustrated embodiment depictsthe downhole tool 108 to be coupled to the drill string 104 furtherdownhole than the downhole sub 104, in other embodiments, the downholesub 102 may comprise a portion of the downhole tool 108, the downholesub 102 may be coupled to the drill string 104 further downhole than thedownhole sub 104, a combination of these, or the like. The downhole tool108 may comprise any of a number of different types of tools includingMWD (measurement while drilling) tools, LWD (logging while drilling)tools, and others.

The downhole friction control system 100 generally comprises a vibrationcomponent 110. The vibration component 110 is mechanically coupled tothe downhole sub 102 to generate a selected vibration 112 in the drillstring 104 when the downhole sub 102 is attached to the drill string104. The vibration component 110 may comprise, for example, a fluttervalve, a motor, a piezoelectric device, a combination of these, or thelike. In at least one example, the vibration component 110 comprises amotor coupled to the drill string 104 and to an eccentric weight. In atleast one embodiment, the vibration component 110 comprises a motor witha rotor that is off balance via a counterweight. In some examples, thevibration component 110 adjusts vibration by varying the speed of themotor or shifting the weight of the counterbalance, for example closerto or further from the center of rotation. In some embodiments, thevibration component 110 may comprise multiple elements capable ofcausing vibration. In some embodiments, the location at which thevibration component 110 is coupled to the downhole sub 102 is chosenbased on the type of tool, the type of vibration component 110, theselected vibration 112, the type of solids that are expected downhole, acombination of these, or the like.

The selected vibration 112 may be selected based on any of a variety ofcriteria, for example, a desired level, a desired frequency, a desiredlateral movement 114 of a portion of the friction control system 100, adesired reduction of operational friction of the downhole tool 108, adesired reduction of pressure at the downhole tool 108, to dislodgeaccumulated solids 116, to prevent accumulation of solids 116, acombination of these, or the like. In at least one embodiment, theselected vibration 112 is sufficient to impart a lateral movement 114 ofat least 5 mm of a portion of the drill string 104. For example, in atleast one embodiment, the selected vibration 112 applied to a 4-inchdiameter drill string 104 achieves the intended lateral movement 114(e.g., at least 5 mm) of the drill string approximately one-half meterfrom the vibration component 110. In at least one embodiment, theselected vibration 112 is selected based on a desired vibration level.In some embodiments, the selected vibration 112 comprises a frequency offrom about 20 Kilohertz to about 60 Kilohertz. In some embodiments, theselected vibration 112 is sufficient to dislodge accumulated solids 116from certain components of the drill string 104, for example, filters,valves, the tool 108, pistons, screens, moving mandrels, a combinationof these, or the like.

In at least one embodiment, the tool 108 is coupled to the downhole sub102, and the selected vibration 112 is sufficient to reduce operationalfriction between components of the downhole tool 108. For example, in adrilling operation, the amount of friction can be measured in terms oftorque needed to turn the drill string, and when the torque becomesgreater than some desired level, or increases at a greater rate than isexpected, friction reduction can be employed until the torque is reducedby some desired amount. In at least one embodiment, the downhole tool108 comprises a cutting tool, and the selected vibration 112 issufficient to reduce the pressure of the cutting tool. In someembodiments, the selected vibration 112 increases efficiency of thedownhole tool 108. For example, in the case of a cutting tool,application of the selected vibration 112 can allow the cutting tool toremove the same amount of material per unit period of time with reducedcutting pressure, thereby increasing the efficiency of the cutting tool.This can reduce the risk of damage or wear to the downhole tool 108 dueto pressure.

In some embodiments, the downhole friction control system 100 comprisesone or more sensors 118 to monitor one or more components of thedownhole friction control system 100. For example, in at least oneembodiment, one or more sensors 118 monitor the selected vibration 112produced by the vibration component 110. In some embodiments, one ormore sensors 118 monitor relative location of two or more surfaces orcomponents. For example, in at least one embodiment, one or more sensors118 monitor relative positions of two downhole movable surfaces, suchthat the one or more sensors 118 can identify operational frictionissues based on whether the two downhole surfaces are moving relative toone another.

In some embodiments, the downhole friction control system 100 comprisesa controller 120 in communication with the vibration component 110. Inat least one embodiment, the controller 120 is located at a surface ofthe earth while in communication with the downhole vibration component110. In some embodiments, the controller 120 is to adjust the selectedvibration 112 (e.g., level, frequency, etc.). In at least oneembodiment, the controller 120 is in communication with the one or moresensors 118, such that the controller 120 is to adjust the selectedvibration 112 based on information received from the one or more sensors118. For example, in at least one embodiment the one or more sensors 118monitor relative positions of two downhole movable surfaces, and thecontroller 120 activates or increases the selected vibration 112 if theone or more sensors 118 identify that the two downhole movable surfacesare prevented from moving due to operational friction engagement. Insome embodiments, the controller 120 stops, decreases, or otherwiseadjusts the selected vibration 112 responsive to disengagement of thetwo downhole movable surfaces (for example, as indicated by the one ormore sensors 118).

In some embodiments, the controller 120 controls the selected vibration112 by adjusting the level of the vibration, frequency of the vibration,duration of the vibration, a combination of these, or the like. In atleast one embodiment, the controller 120 adjusts the selected vibration112 to target specific kinds of solids 116, based on the type of tool108, or both. In at least one embodiment, a lookup table is used totarget solids in a specific area of the drill string. In someembodiments, the controller 120 periodically references the lookup tableto determine the selected vibration 112. In at least one embodiment, thecontroller 120 adjusts the selected vibration 112 according to aschedule, for example, activate a first selected vibration 112 for tenseconds, stop the vibration component 110 for one minute, activate asecond selected vibration for thirty seconds, stop the vibrationcomponent 110 for ten seconds, and repeat. In at least one embodiment,the controller 120 starts, stops, or otherwise adjusts the vibrationautomatically in response to a signal from the one or more sensors 118that a measurement exceeds a predetermined threshold. In someembodiments, the controller 120 can control the selected vibration 112under one or more of a variety of modes, for example, variableamplitude, variable frequency, pulsing, cycling, ramping up, rampingdown, a combination of these, or the like.

FIG. 2 depicts an example downhole friction control system 200 in usewith a ball valve 202 in a closed position, in accordance with someembodiments. In at least one embodiment, the ball valve 202 comprises atleast a portion of a downhole cutting tool, used for example, to cutthrough coil tubing. In some embodiments, a downhole sub 204, attachedto a drill string 206, comprises a portion of the downhole cutting tool.The ball valve 202 is shown in the closed position, such that an opening208 is not positioned within the drill string 206, and such that theball valve 202 is blocking flow within the drill string 206. To open theball valve 202, pressure is applied to an open line 210, while a closeline 212 is vented.

In at least one embodiment, one or more vibration components 214, 215are coupled to the downhole sub 204. In some embodiments, the one ormore vibration components 214, 215 are to generate a selected vibration218 in the drill string 206. In at least one embodiment, the selectedvibration 218 is selected to dislodge accumulated solids 220. In atleast one embodiment, the selected vibration 218 is selected to reducepressure at the ball valve 202. The one or more vibration components214, 215 may each comprise an oscillating or fluttering device, a motor,a piezoelectric device, or the like. For example, in at least oneembodiment, the vibration component 214 comprises a flutter valve, suchthat when pressure is applied to the open side 210, the flutter valvegenerates the selected vibration 218. In some embodiments, the selectedvibration 218 generated by the flutter valve 214 is sufficient todislodge accumulated solids 220. In some embodiments, the selectedvibration 218 allows the ball valve 202 to open with less pressureapplied to the open line 210. In some embodiments, a controller is usedto adjust the selected vibration 218.

In the illustrated embodiment, the one or more vibration components 214,215 comprise vibration motors or piezoelectric devices coupled to thedownhole sub 204 on opposite sides of the ball valve 202. The one ormore vibration components 214, 215 can operate alone or together togenerate the selected vibration 218. In at least one embodiment, theselected vibration 218 generated by the vibration motors orpiezoelectric devices 214, 215, is sufficient to dislodge accumulatedsolids 220. In some embodiments, the one or more vibration components214, 215 generate the selected vibration 218 to reduce operationalfriction of the ball valve 202 as it opens.

FIG. 3 depicts the example downhole friction control system 200 of FIG.2 with the ball valve 202 in the open position, in accordance with someembodiments. The ball valve 202 is shown in the open position, such thatthe opening 208 (see FIG. 2) is positioned within the drill string 206,and such that the ball valve 202 is permitting flow within the drillstring 206. To close the ball valve 202, pressure is applied to theclose line 212, while the open line 210 is vented. In at least oneembodiment, the ball valve 202 comprises at least a portion of adownhole cutting tool, used for example, to cut through coil tubing 302.

In the illustrated embodiment, the coil tubing is positioned inside thedrill string 206, such that it extends through the opening 208 of theball valve 202. In at least one embodiment, when pressure is applied tothe close line 212, and the open line 210 is vented, an edge of theopening 208 of the ball valve 202 cuts the coil tubing 302. In such anembodiment, the vibration component 215 can comprise a flutter valve orother oscillating device, such that as pressure is applied to the closeline 212, the flutter valve generates the selected vibration 218, toincrease the efficiency of the cutting ball valve 202. In someembodiments, one or more vibration components 214, 215 comprise motorsor piezoelectric devices to generate the selected vibration 218 toincrease the efficiency of the cutting ball valve 202. In at least oneembodiment, the selected vibration 218 allows the cutting ball valve 202to cut the coiled tubing 302 at the same speed, or in the same amount oftime, with reduced pressure applied to the close line 212. In at leastone embodiment, the selected vibration 218 is sufficient to dislodgeaccumulated solids 220. In at least one embodiment, the selectedvibration 218 is selected to reduce operational friction of the ballvalve 202 as it closes.

FIG. 4 is a flow diagram of an example method 400 of downhole frictioncontrol, in accordance with some embodiments. As a matter ofconvenience, the method 400 is described with reference to the downholefriction control system 100 of FIG. 1. At block 402 a downhole tool 108is operated. For example, in at least one embodiment, the downhole tool108 comprises a cutting tool and is operated to cut a downhole object.In at least one embodiment, the downhole tool 108 is located proximateto a downhole sub 102 comprising a vibration component 110. In at leastone embodiment, the vibration component is coupled to the downhole sub102. In some embodiments, the vibration component 102 is mechanicallycoupled to a portion of a drill string. In some embodiments, thedownhole sub 102 comprises a portion of the downhole tool 108.

At block 404, a selected vibration 112 is introduced by the vibrationcomponent 110 to reduce operational friction of the downhole tool 108.The vibration component 110 may comprise, for example, a flutter valveor other oscillating device, a motor coupled to the drill string and toan eccentric weight, one or more valves, a piezoelectric device, acombination of these, or the like, such that introducing the selectedvibration 112 comprises actuating the vibration component 110. In atleast one embodiment, introducing the selected vibration 112 comprisescycling hydraulic pressure via one or more valves. In at least oneembodiment, the vibration component 110 generates a selected vibration112 that represents a high frequency pulse. In at least one embodiment,introducing the selected vibration 112 increases the cutting efficiencyof the downhole tool 108. For example, the tool 108 can cut the sameamount of material per unit time with reduced cutting pressure by addingthe selected vibration 112. In some embodiments, introducing theselected vibration 112 dislodges accumulated solids 116 at the downholetool 108, drill string 104, downhole sub 102, another downholecomponent, a combination of these, or the like. In some embodiments, theselected vibration 112 is introduced before the tool 108 is operated.

At block 406 one or more downhole friction factors are monitored via oneor more sensors 118. For example, in at least one embodiment, the one ormore sensors 118 monitor relative positions of two or more downholemovable surfaces. In some embodiments, the sensors 118 measure two ormore downhole movable surfaces prevented from moving due to operationalfriction engagement. In some examples, the one or more sensors 118monitor the selected vibration 112 produced by the vibration component110. In at least one embodiment, the one or more sensors 118 monitor thelateral movement or displacement 114 of one or more downhole components.In some embodiments, the one or more sensors 118 monitor one or moreparameters associated with solids. For example, in some embodiments, theone or more sensors could monitor accumulation of solids, type ofsolids, location of solids, density of solids, speed of solid flow, acombination of these, or the like. Each of the actions shown in themethod 400 are optional, and thus, some embodiments of the method 400 donot include monitoring the one or more downhole friction factors.

At block 408 the selected vibration 112 is controlled via a controller120. In some embodiments, the controller 120 adjusts the selectedvibration 112 responsive to information received from the one or moresensors 118. In some embodiments, the controller 120 adjusts theselected vibration 112 responsive to disengagement of surfaces monitoredby the one or more sensors 118. In some embodiments, the controller 120controls the selected vibration 112 by adjusting the level or frequencyof vibration. In some embodiments the controller 120 adjusts theselected vibration 112 according to a preset mode or sequence. In someembodiments, the controller 120 controls the selected vibration 112 bystopping vibration, or initiating vibration at the vibration component.In at least one embodiment, the selected vibration 112 patterns arepreset and do not include a controller 120 capable of adjusting theselected vibration 112.

FIG. 5 is a diagram showing a wireline system 500 embodiment, and FIG. 6is a diagram showing a logging while drilling (LWD) system 600embodiment. The systems 500, 600 may thus comprise portions of awireline logging tool body 502 as part of a wireline logging operation,or of a down hole tool 602 as part of a down hole drilling operation.

FIG. 5 illustrates a well used during wireline logging operations. Inthis case, a drilling platform 504 is equipped with a derrick 506 thatsupports a hoist 508. Drilling oil and gas wells is commonly carried outusing a string of drill pipes connected together so as to form adrillstring that is lowered through a rotary table 510 into a wellboreor borehole 512. Here it is assumed that the drillstring has beentemporarily removed from the borehole 512 to allow a wireline loggingtool body 502, such as a probe or sonde, to be lowered by wireline orlogging cable 514 (e.g., slickline cable) into the borehole 512.Typically, the wireline logging tool body 502 is lowered to the bottomof the region of interest and subsequently pulled upward at asubstantially constant speed. The tool body 502 may include downholefriction control system 516 (which may include any one or more of theelements of systems 100, 200 or 300 of FIGS. 1-3).

During the upward trip, at a series of depths various instruments (e.g.,co-located with the downhole friction control system 516 included in thetool body 502) may be used to perform measurements on the subsurfacegeological formations 518 adjacent to the borehole 512 (and the toolbody 502). The measurement data can be communicated to a surface loggingfacility 520 for processing, analysis, and/or storage. The processingand analysis may include natural gamma-ray spectroscopy measurementsand/or determination of formation density. The logging facility 520 maybe provided with electronic equipment for various types of signalprocessing. Similar formation evaluation data may be gathered andanalyzed during drilling operations (e.g., during LWD/MWD (measurementwhile drilling) operations, and by extension, sampling while drilling).

In some embodiments, the tool body 502 is suspended in the wellbore by awireline cable 514 that connects the tool to a surface control unit(e.g., comprising a workstation 522). The tool may be deployed in theborehole 512 on coiled tubing, jointed drill pipe, hard wired drillpipe, or any other suitable deployment technique.

Referring to FIG. 6, it can be seen how a system 600 may also form aportion of a drilling rig 604 located at the surface 606 of a well 608.The drilling rig 604 may provide support for a drillstring 610. Thedrillstring 610 may operate to penetrate the rotary table 510 fordrilling the borehole 512 through the subsurface formations 518. Thedrillstring 610 may include a Kelly 612, drill pipe 614, and a bottomhole assembly 616, perhaps located at the lower portion of the drillpipe 614. As can be seen in the figure, the drillstring 610 may includea downhole friction control system 618 (which may include any one ormore of the elements of system 100, 200 or 300 of FIGS. 1-3).

The bottom hole assembly 616 may include drill collars 620, a down holetool 602, and a drill bit 622. The drill bit 622 may operate to createthe borehole 512 by penetrating the surface 606 and the subsurfaceformations 518. The down hole tool 602 may comprise any of a number ofdifferent types of tools including MWD tools, LWD tools, and others.

During drilling operations, the drillstring 610 (perhaps including theKelly 612, the drill pipe 614, and the bottom hole assembly 616) may berotated by the rotary table 510. Although not shown, in addition to, oralternatively, the bottom hole assembly 616 may also be rotated by amotor (e.g., a mud motor) that is located down hole. The drill collars620 may be used to add weight to the drill bit 622. The drill collars620 may also operate to stiffen the bottom hole assembly 616, allowingthe bottom hole assembly 616 to transfer the added weight to the drillbit 622, and in turn, to assist the drill bit 622 in penetrating thesurface 606 and subsurface formations 518.

During drilling operations, a mud pump 624 may pump drilling fluid(sometimes known by those of ordinary skill in the art as “drillingmud”) from a mud pit 626 through a hose 628 into the drill pipe 614 anddown to the drill bit 622. The drilling fluid can flow out from thedrill bit 622 and be returned to the surface 606 through an annular area630 between the drill pipe 614 and the sides of the borehole 512. Thedrilling fluid may then be returned to the mud pit 626, where such fluidis filtered. In some embodiments, the drilling fluid can be used to coolthe drill bit 622, as well as to provide lubrication for the drill bit622 during drilling operations. Additionally, the drilling fluid may beused to remove subsurface formation cuttings created by operating thedrill bit 622.

The workstation 522 and the controller 526 may include modulescomprising hardware circuitry, a processor, and/or memory circuits thatmay store software program modules and objects, and/or firmware, andcombinations thereof, as desired by the architect of the downholefriction control system 516, 618 and as appropriate for particularimplementations of various embodiments. For example, in someembodiments, such modules may be included in an apparatus and/or systemoperation simulation package, such as a software electrical signalsimulation package, a power usage and distribution simulation package, apower/heat dissipation simulation package, and/or a combination ofsoftware and hardware used to simulate the operation of variouspotential embodiments.

Thus, many embodiments may be realized. Some of these will now be listedas non-limiting examples.

In some embodiments, a system comprises a downhole sub to attach to adrill string and a vibration component mechanically coupled to thedownhole sub to generate a selected vibration in the drill string whenthe downhole sub is attached to the drill string.

In some embodiments, the selected vibration comprises a selected leveland/or frequency of vibration.

In some embodiments, the selected vibration is sufficient to impart alateral movement of a portion of the drill string of at least 5 mm.

In some embodiments, the selected vibration comprises a frequency offrom about 20 Kilohertz to about 60 Kilohertz.

In some embodiments, the selected vibration is selected to reduce thepressure of a downhole cutting tool.

In some embodiments, the system further comprises a downhole toolcoupled to the drill string, wherein the selected vibration is selectedto reduce operational friction between components of the downhole tool.

In some embodiments, the system further comprises a controller to adjustthe selected vibration to dislodge debris accumulated at the downholetool.

In some embodiments, the downhole sub comprises a portion of a downholetool, the selected vibration being selectable to reduce operationalfriction of the downhole tool.

In some embodiments, the vibration component comprises a flutter valve.

In some embodiments, the vibration component comprises a motor.

In some embodiments, the vibration component comprises a piezoelectricdevice.

In some embodiments, a method comprises introducing, via a vibrationcomponent mechanically coupled to a portion of a drill string, aselected vibration to the drill string to reduce operational friction ofa downhole tool.

In some embodiments, the method further comprises operating the downholetool to cut a downhole object, wherein introducing the selectedvibration increases cutting efficiency of the downhole tool.

In some embodiments, the method further comprises operating the downholetool, wherein introducing the selected vibration dislodges accumulateddebris from the downhole tool.

In some embodiments, introducing the selected vibration comprisesactuating a flutter valve coupled to the drill string.

In some embodiments, introducing the selected vibration comprisesactuating a motor coupled to the drill string and to an eccentricweight.

In some embodiments, introducing the selected vibration comprisesactuating a piezoelectric device coupled to the drill string.

In some embodiments, introducing the selected vibration comprisescycling hydraulic pressure via one or more valves.

In some embodiments, the method further comprises monitoring relativepositions of two downhole movable surfaces prevented from moving due tooperational friction engagement, and adjusting the selected vibrationresponsive to disengagement of the two downhole movable surfaces.

In some embodiments, the method further comprises controlling theselected vibration by adjusting the level or frequency of vibration.

In the foregoing Detailed Description, it can be seen that variousfeatures are grouped together in a single embodiment for the purpose ofstreamlining the disclosure. This method of disclosure is not to beinterpreted as reflecting an intention that the claimed embodimentsrequire more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive subject matter lies in lessthan all features of a single disclosed embodiment. Thus the followingclaims are hereby incorporated into the Detailed Description, with eachclaim standing on its own as a separate embodiment.

Note that not all of the activities or elements described above in thegeneral description are required, that a portion of a specific activityor device may not be required, and that one or more further activitiesmay be performed, or elements included, in addition to those described.Still further, the order in which activities are listed are notnecessarily the order in which they are performed. Also, the conceptshave been described with reference to specific embodiments. However, oneof ordinary skill in the art appreciates that various modifications andchanges can be made without departing from the scope of the presentdisclosure as set forth in the claims below. Accordingly, thespecification and figures are to be regarded in an illustrative ratherthan a restrictive sense, and all such modifications are intended to beincluded within the scope of the present disclosure.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any feature(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature of any or all the claims. Moreover, the particular embodimentsdisclosed above are illustrative only, as the disclosed subject mattermay be modified and practiced in different but equivalent mannersapparent to those skilled in the art having the benefit of the teachingsherein. No limitations are intended to the details of construction ordesign herein shown, other than as described in the claims below. It istherefore evident that the particular embodiments disclosed above may bealtered or modified and all such variations are considered within thescope of the disclosed subject matter. Accordingly, the protectionsought herein is as set forth in the claims below.

What is claimed is:
 1. A system, comprising: a downhole sub to attach toa drill string; and a vibration component mechanically coupled to thedownhole sub to generate a selected vibration in the drill string whenthe downhole sub is attached to the drill string.
 2. The system of claim1, wherein the selected vibration comprises a selected level and/orfrequency of vibration.
 3. The system of claim 1, wherein the selectedvibration is sufficient to impart a lateral movement of a portion of thedrill string of at least 5 mm.
 4. The system of claim 3, wherein theselected vibration comprises a frequency of from about 20 Kilohertz toabout 60 Kilohertz.
 5. The system of claim 1, wherein the selectedvibration is selected to reduce the pressure of a downhole cutting tool.6. The system of claim 1, further comprising: a downhole tool to coupleto the drill string, wherein the selected vibration is selected toreduce operational friction between components of the downhole tool. 7.The system of claim 6, further comprising: a controller to adjust theselected vibration to dislodge debris accumulated at the downhole tool.8. The system of claim 1, wherein the downhole sub comprises a portionof a downhole tool, the selected vibration being selectable to reduceoperational friction of the downhole tool.
 9. The system of claim 1,wherein the vibration component comprises a flutter valve.
 10. Thesystem of claim 1, wherein the vibration component comprises a motor.11. The system of claim 1, wherein the vibration component comprises apiezoelectric device.
 12. A method, comprising: introducing, via avibration component mechanically coupled to a portion of a drill string,a selected vibration to the drill string to reduce operational frictionof a downhole tool.
 13. The method of claim 12, further comprising:operating the downhole tool to cut a downhole object, whereinintroducing the selected vibration increases cutting efficiency of thedownhole tool.
 14. The method of claim 12, further comprising: operatingthe downhole tool, wherein introducing the selected vibration dislodgesaccumulated debris from the downhole tool.
 15. The method of claim 12,wherein introducing the selected vibration comprises actuating a fluttervalve coupled to the drill string.
 16. The method of claim 12, whereinintroducing the selected vibration comprises actuating a motor coupledto the drill string and to an eccentric weight.
 17. The method of claim12, wherein introducing the selected vibration comprises actuating apiezoelectric device coupled to the drill string.
 18. The method ofclaim 12, wherein introducing the selected vibration comprises cyclinghydraulic pressure via one or more valves.
 19. The method of claim 12,further comprising: monitoring relative positions of two downholemovable surfaces having a reduced relative movement range due tooperational friction engagement; and adjusting the selected vibrationresponsive to increase in the relative movement range of the twodownhole movable surfaces.
 20. The method of claim 12, furthercomprising: controlling the selected vibration by adjusting the level orfrequency of vibration.